A major concern during surgical procedures as well as other medical operations is carrying out the procedures with as much precision as is possible. For example, in orthopedic procedures, less than optimum alignment of implanted prosthetic components may cause undesired wear, which may eventually lead to the failure of the implanted prosthesis and necessitate revision. Other general surgical procedures, such as body exploration from penetrating trauma, implant placement and neoplasm surgery, also require precision in their execution.
With orthopedic procedures, previous practices have made precise alignment of prosthetic components challenging. For example, in a total knee arthroplasty, previous instrument design for resection of bone limited the alignment of the femoral and tibial resections to average values for varus/valgus, flexion/extension and external/internal rotation. Additionally, surgeons often use visual landmarks or “rules of thumb” for alignment, which can be misleading due to anatomical variability. Intramedullary referencing instruments are also undesirable because they violate the femoral and tibial canals, increasing the risk of fat embolism and unnecessary blood loss in the patient. Similar problems may also be encountered in other procedures, such as the replacement of hip and shoulder joints as well as the insertion of an intramedullary canal nail into a weakened or broken bone.
Several manufacturers currently produce image-guided surgical navigation systems that are used to assist in performing surgical procedures with greater precision. The TREON™ and iON™ systems with FLUORONAV™ software manufactured by Medtronic Surgical Navigation Technologies, Inc. are examples of such systems. The BrainLAB VECTORVISION™ system is another example of such a surgical navigation system. Systems and processes for accomplishing image-guided surgery are also disclosed in U.S. Ser. No. 10/084,012, filed Feb. 27, 2002 and entitled “Total Knee Arthroplasty Systems and Processes”; U.S. Ser. No. 10/084,278, filed Feb. 27, 2002 and entitled “Surgical Navigation Systems and Processes for Unicompartmental Knee Arthroplasty”; U.S. Ser. No. 10/084,291, filed Feb. 27, 2002 and entitled “Surgical Navigation Systems and Processes for High Tibial Osteotomy”; International Application No. US02/05955, filed Feb. 27, 2002 and entitled “Total Knee Arthroplasty Systems and Processes”; International Application No. US02/05956, filed Feb. 27, 2002 and entitled “Surgical Navigation Systems and Processes for Unicompartmental Knee Arthroplasty”; International Application No. US02/05783 entitled “Surgical Navigation Systems and Processes for High Tibial Osteotomy”; U.S. Ser. No. 10/364,859, filed Feb. 11, 2003 and entitled “Image Guided Fracture Reduction,” which claims priority to U.S. Ser. No. 60/355,886, filed Feb. 11, 2002 and entitled “Image Guided Fracture Reduction”; and U.S. Ser. No. 60/271,818, filed Feb. 27, 2001 and entitled “Image Guided System for Arthroplasty”; U.S. Ser. No. 10/229,372, filed Aug. 27, 2002 and entitled “Image Computer Assisted Knee Arthroplasty”, the entire contents of each of which are incorporated herein by reference as are all documents incorporated by reference therein.
These systems and processes use position and/or orientation tracking sensors such as infrared sensors acting in a stereoscopic manner or other sensors acting in conjunction with reference structures or reference transmitters to track positions of body parts, surgery-related items such as implements, instruments, trial prosthetics, prosthetic components, and virtual constructs or references such as rotational axes which have been calculated and stored based on designation of bone landmarks. Processing capability such as any desired form of computer functionality, whether standalone, networked, or otherwise, takes into account the position and orientation information as to various items in the position sensing field (which may correspond generally or specifically to all or portions or more than all of the surgical field) based on sensed position and orientation of their associated reference structures such as fiducials, reference transmitters, or based on stored position and/or orientation information. The processing functionality correlates this position and orientation information for each object with stored information, such as a computerized fluoroscopic imaged file, a wire frame data file for rendering a representation of an instrument component, trial prosthesis or actual prosthesis, or a computer generated file relating to a rotational axis or other virtual construct or reference. The processing functionality then displays position and orientation of these objects on a screen or monitor. Thus, these systems and processes, by sensing the position of reference structures or transmitters, can display or otherwise output useful data relating to predicted or actual position and orientation of body parts, surgically related items, implants, and virtual constructs for use in navigation, assessment, and otherwise performing surgery or other operations.
Some of these reference structures or reference transmitters may emit or reflect infrared light that is then detected by an infrared camera. The references may be sensed actively or passively by infrared, visual, sound, magnetic, electromagnetic, x-ray, or any other desired technique. An active reference emits energy, and a passive reference merely reflects energy. In some embodiments, the reference structures have at least three, but usually four, markers or fiducials that are tracked by an infrared sensor to determine the position and orientation of the reference and thus the position and orientation of the associated instrument, implant component or other object to which the reference is attached.
The Medtronic imaging systems allow reference structures to be detected at the same time the fluoroscopy imaging is occurring. This allows the position and orientation of the reference structures to be coordinated with the fluoroscope imaging. Then, after processing position and orientation data, the reference structures may be used to track the position and orientation of anatomical features that were recorded with a fluoroscope. Computer-generated images of instruments, components, or other structures that are fitted with reference structures may be superimposed on the fluoroscopic images. The instruments, trial, implant or other structure or geometry can be displayed as 3-D models, outline models, or bone-implant interface surfaces.
The reference structures described above are an important component of these systems and processes. FIG. 1 shows a reference structure 8 secured to a bone. FIG. 2 shows reference structures 8 as used in a surgical setting. In some systems, a reference transmitter, as opposed to a passive reference structure, actively transmits position and orientation data to the tracking system. FIG. 3 shows a reference transmitter or receiver 10 secured to a bone that is useable with such systems.
Systems such as the Medtronic system may monitor the location and orientation of the reference structures 8, and consequently the portion of the anatomy or instruments secured to the reference structure 8, by either actively or passively detecting the position of fiducials 12 shown in FIGS. 1 and 2 associated with the reference structure 8. Because the fiducials 12 can be arranged in particular patterns, the system can determine the exact orientation and location of the reference structure 8 associated with the fiducials 12. In other words, depending upon the particular location of the individual fiducials 12, the system will “see” the reference structure 8 in a particular way and will be able to calculate the location and orientation of the reference structure based upon that data. Consequently, the system can determine the exact orientation and location of the portion of the anatomy or instrument associated with and connected to the reference structure 8.
As discussed above, the exact spatial relationship of the individual fiducials 12 with respect to each other and the associated anatomy or instrument forms the basis of how a fiducial-based system calculates the position and orientation of the associated items. Similarly, the exact spatial relationship of a reference transmitter or receiver 10 with respect to its associated anatomy or instrument forms the basis of how a transmitter-based system calculates the position and orientation of the associated anatomy or instruments. Consequently, once the spatial relationship of the fiducials 12 or reference transmitter or receiver 10 with respect to the associated item to be tracked has been registered in the system, subsequent changes in the position and/or orientation of the fiducials 12 or reference transmitter 10 may cause the system to erroneously calculate the position and orientation of the anatomy or instruments associated with the fiducials 12 or reference transmitter 10. Even minor changes in orientation and/or position of the references may lead to dramatic differences in how the system detects the orientation and/or location of the associated anatomy or instruments. Such changes may require the system to be recalibrated, requiring additional fluoroscopy or other imaging to be obtained, increasing the time and the expense of the procedure. Failure to recalibrate the system may lead to imprecision in the execution of the desired surgical procedure.
The references 8 and 10 shown in FIGS. 1-3 may be undesirable because they may be particularly vulnerable to change of location and/or orientation with respect to their associated instrument or anatomy. This may be especially problematic in busy operating rooms, where several people are working at once. References 8 and 10 may be particularly susceptible to being bumped, dislodged, or otherwise misplaced because they are cumbersome and prone to interfering with the surgical procedure because of their size. The references may also be susceptible to change in location and/or orientation because they are secured at a single location by a column or other structure to the bony anatomy, instruments, or other structure and are distanced from the anatomy to which they are attached.
Some reference structures do not allow the repositioning or removal of individual fiducials with respect to the reference structure. This may be problematic because there may be times when it is desirable to place the reference structure in a location and orientation that can be effectively visualized and tracked by the system, yet remain out of the way of the surgeon. Moreover, reference structures that do not allow removal of the fiducials from the remainder of the reference structure prevent defective or inoperative fiducials from being replaced without replacing the entire reference structure.
Another major concern with carrying out surgeries and other medical operations with absolute precision is precisely targeting, aligning and/or navigating instruments with or without the assistance of image-guided surgical navigation systems. Problematically, during surgery a surgeon may need to use one hand to stabilize an instrument while using the other hand to target, align and/or navigate the instrument. If the surgeon is the sole means for stabilizing as well as aligning/navigating/targeting the instrument, distractions to the surgeon may result in the instrument becoming misaligned, increasing the chances for surgical error and/or increasing procedural tedium. For instance, if the surgeon looks away from the instrument to view a monitor, the surgeon may inadvertently move his or her hands, causing the instrument to move relative to the anatomy.
Some efforts to alleviate the above difficulties include the use of robotic arms. However, robotic arms may require the navigation of the instrument to be programmed and consequently executed without surgeon input during the robotic portion of the procedure. These robotic arms may be undesirable because they prevent the surgeon from using his or her intuition and experience to target, align and/or navigate the instrument. Additionally, these robotic arms prevent the surgeon from receiving tactile feedback, an important part of some surgical procedures. In addition, robots generally operate much more slowly than a skilled surgeon.
Other, non-robotic, instrument mounting arms have also been used to lock a navigated instrument into position. In addition to the other problems mentioned above, some previous instrument mounting arms may be undesirable because readjustment of the instrument, once locked into place, requires unlocking the arm. Unlocking the arm may increase the tedium of the procedure.